1. Field of the Invention
The present invention relates to an image forming unit of an electrophotographic image forming apparatus and, more particularly, to an apparatus for discharging waste toner produced in an image forming unit.
2. Description of the Related Art
In general, an electrophotographic image forming apparatus includes an image forming unit to form a desired image by receiving a signal from, for example, a computer, a paper supplying unit to supply paper on which the desired image will be transferred, and a fixing unit to fix the transferred image on the paper.
An example of an image forming unit 10 for producing an image on paper is shown in FIG. 1.
A laser beam scanned from a laser scan unit 11 creates an electrostatic latent image on a photosensitive medium 12. The electrostatic latent image formed on the photosensitive medium 12 is developed into a visible image by toner 15 supplied by a developing roller 14. The developed visible image is transferred to paper 1 supplied from a paper supply unit (not shown) by a transfer roller 16. After the transfer of the visible image, the remaining toner (hereinafter referred to as “waste toner”) is separated from the photosensitive medium 12 by a waste toner cleaner 18. The separated toner (i.e., waste toner 42) is discharged out of a housing 19 by a waste toner discharge apparatus 20.
Referring to FIG. 2, the waste toner discharge apparatus 20 includes an auger 30 disposed under and parallel to the waste toner cleaner 18, an auger supporting member 22 having a waste toner discharge port 24 supporting the rotational movement of the auger 30, a shutter 26 rotatably disposed at a side of the auger supporting member 22 opposite the auger 30 for opening and closing the waste toner discharge port 24, a lever 28 disposed at a side of the shutter 26 opposite the auger supporting member 22, and a projection 32 disposed at a position interfering with the lever 28 when the image forming unit 10 is mounted on a frame 50 (FIG. 1).
When the image forming unit 10 is mounted on the frame 50, the shutter 26 rotates around the circumference of the auger supporting member 22 via the projection 32 to expose the waste toner discharge port 24 thereby opening the waste toner discharge apparatus 20.
Thus, the waste toner 42 separated by the waste toner cleaner 18 is moved to the auger supporting member 22 by the auger 30 and discharged out of the housing 19 through the waste toner discharge port 24. A waste toner container 40 is disposed under the waste toner discharge port 24 and the discharged waste toner 42 is collected in the waste toner container 40.
When the photosensitive medium 12 is changed or the waste toner container 40 is emptied, the image forming unit 10 is disassembled from the frame. If the image forming unit 10 is raised, the lever 28 of the waste toner discharge apparatus 20 is no longer held in place by the projection 32, and the shutter 26 rotates in reverse by a torsion spring (not shown) between the shutter 26 and the auger supporting member 22 to cover the waste toner discharge port 24 (FIG. 3). Therefore, the waste toner 42 remaining in the housing 19 of the image forming unit 10 does not flow out and the image forming unit 10 can be freely disassembled and treated.
However, in the waste toner discharge apparatus 20 with a shutter 26 that returns via a torsion spring, as described above, the shutter 26 may fail to completely cover the waste toner discharge port 24 when the torsion spring is transformed. Also, when the waste toner 42 collects around the waste toner discharge port 24, frictional resistance between the auger supporting member 22 and the shutter 26 increases and, hence, the action of the torsion spring may not cause the shutter 26 to completely cover the waste toner discharge port. When the shutter 26 fails to completely cover the waste toner discharge port 24, the waste toner 42 leaks out upon disassembly/assembly of the image forming unit 10, thereby causing contamination of the image forming apparatus.
Further, even when the image forming unit 10 is disassembled, while the shutter 26 of the waste toner discharge apparatus 20 is completely closed, the projecting lever 28 may be inadvertently pushed by a user. If the lever 28 is pushed, the shutter 26 will move and, consequently, the waste toner discharge port 24 is opened and the waste toner 42 remaining in the housing 19 flows out, causing contamination of the surroundings.